This invention relates generally to medical procedures such as hemodialysis in which blood is drawn from a blood vessel for treatment by an artificial kidney machine, and returned to a patient whose kidneys are unable to properly cleanse the blood. In dialysis, as this procedure is called, two needles are inserted in separate blood vessels, and connected by sterile rubber-like or plastic tubing to inlet and outlet ports of an artificial kidney machine.
Because of the large volume of blood that must be handled, and the several hours time required for each treatment, the needles are very large. Typically, they are made of steel tubing up to 15-gauge in size (approximately 1/12th inch diameter) sharpened by making a double bevel cut across their forward end.
A kidney dialysis patient must undergo this treatment as often as three times a week, sometimes every other day, and as much as four hours each time. The repeated penetration of the blood vessels by these large relatively dull needles is exceedingly painful and causes severe trauma to the blood vessels and overlying tissues. Favored locations for the needles are in the forearm where they are inserted into four- to six-inch segments of the blood vessels themselves, or in substitute sections called "Gortex" or "Bovine" grafts.
Various locations in the forearm, the upperarm and the legs are used as access points for dialysis needles. Healing is often slow because the blood chemistry of dialysis patients is not ideal for rapid healing. If the patient's blood vessels fail to regenerate themselves, or scar tissue from repeated needle insertions prevents adequate blood flow, the blood vessels are in effect worn out, the patient has no more access points, and he or she dies.
There are several problems inherent in these conventional large diameter, bevel cut dialysis needles.
In the first place, these large 15-gauge needles simply cannot be sharpened effectively by the bevel-cut method. This method works well on small hypodermic needles of 27-gauge (1/60th inch diameter) or smaller. However, the bevel-sharpening technique does not operate effectively on large diameter dialysis needles; this technique does not make them sharp enough to avoid painful penetration, and trauma to the tissues and blood vessels.
Another problem arises out of the necessity to thread the dialysis needle a full inch or more into the blood vessel to stabilize it for the hours-long procedure. This is difficult to do because the large-diameter needle is roughly the size of the inside diameter of the blood vessel, and the sharpened tip, which is offcenter of the conventional needle, tends to get caught in the blood vessel wall and go right on through the other side. This is a serious, common mishap called "infiltration".
Another problem with the conventional needles is that after they are in place and the dialysis machine in operation, the fluid volume of blood in the patient decreases. The blood pressure then falls and the vein containing the withdrawal needle may collapse across the beveled opening at the front of the needle, acting like a check or flap valve and shutting off flow. When this happens, the machine goes into an alarm condition and the operator or attendant has to take emergency countermeasures to re-start normal flow.
Despite the before-mentioned drawbacks, the only dialysis needles in common use are the bevel-cut tubes described.